A weighty question
In a car crash, size matters
It seems like a quaint thought from a bygone age: an old advertisement lists the attributes of the AMC Gremlin and one of them is weight.
“Weighs more than other small cars,” chirps the cheerful copy. In the back of what would prove to be the poster car for automotive humdrum, a kid plays with a baseball glove, and a golden retriever pants in the trunk. A picture of safe family life, 1970s style.
We now know that the Gremlin was pretty mediocre. We also know that mass isn’t a selling feature; it is far more likely for any modern commercial to trumpet the weight savings found in the use of composite materials. Save weight, save gas, improve handling. But here’s the thing: what if those old copywriters were right? What if heavier is safer?
Pull up the website for the Insurance Institute for Highway Safety (IIHS), and you’ll find the usual vehicle-safety ratings and other consumer advice. But dig a little deeper and you’ll find some troubling information on vehicle weight and fatalities. The question is asked: “Are people less likely to be killed or injured in a bigger, heavier vehicle?” The answer? A simple yes.
However, there’s more to it than just David versus Goliath. The IIHS also published a study in 2011 that seemed to indicate heavier equalled safer for vehicles that were similar in size. A hybrid version of a Toyota Camry, for instance, is about 10 per cent heavier than its pure-gasoline version, but has roughly the same safety features, and according to the study, your odds of sustaining an injury in a crash were 25 per cent lower in the hybrid version than in its standard crossover and sedan counterparts.
So, should we all run to Home Depot and fill our trunks with bags of cement? Well, not quite. Like all statistics, there’s enough going on here that sifting through the data will take a little more work.
First, the obvious. A bigger vehicle means the collision is happening farther from the passenger compartment. It means longer crumple zones to absorb energy, and potentially more metal in the cage surrounding you. A taller vehicle means a higher beltline as well, and according to the IIHS’s studies, based on vehicle size, the number of fatalities per million lowers as your vehicle’s footprint gets larger.
It should, however, be noted that the gap gets narrower as vehicle age decreases. In the late 1970s, there was a huge gulf between a big car and a small one in terms of lethality; with a modern car, size seems to make less of a difference. Improved crumple zones and the use of high-strength materials underline how important vehicle design is in reducing injury in a crash. It’s not just the amount of steel in the car, it’s the way it’s laid out.
Let’s look at a collision between a pickup truck and a mid-size car. The two top-selling passenger vehicles in the Canadian market are the Ford F-150 and the Honda Civic; both are Top Safety Picks from the IIHS, but which one is safest?
A decade or more ago, it wouldn’t be the mass difference between the two vehicles that would inform the outcome, but something safety researchers call “aggressivity.” Put simply, in a collision between a highriding truck or SUV and a normal-height car, the truck’s frame rails could act like the tines of a forklift, or the truck could simply override the car, missing the impact areas and hitting the greenhouse. These days a normal-height pickup must conform to safety regulations, and thus is less damaging to vehicles it hits. Always assuming, of course, that some urban cowboy hasn’t jacked up the thing on a set of 33-inchers and bolted on a Baja-style steel bumper.
Still, the smaller car is at a disadvantage in several ways. First, as it’s lighter, it’s entirely possible for the smaller passenger car to be pushed into traffic, suffering a second collision. Second, common-sense conclusions around vehicle footprint still apply: If you rear-end a pickup truck with something Toyota Corolla-sized, you’ll likely not get past the bed.
But then there are arguments to be made that the smaller car might have avoided the accident in the first place. Greater agility is one factor, but so is the spreading availability of collision-avoidance and mitigation systems. Automatic braking might not help you avoid being rear-ended, but systems to lock up the brakes of a car once a collision has been detected might keep you out of the oncoming lane.
Further, to go back to what the IIHS study on hybrid accidents showed, it’s perhaps not so much about the weight of the cars involved as the way in which they’re driven. Chances are, the person who pays the premium for the hybrid Camry instead of plumping for the 268-horsepower V-6 just might drive a little slower.
Like fuel economy ratings, crash-test results aren’t a perfect read of what might happen in the real world, but they do provide a general guideline. A car that gets high safety ratings in crash testing is probably safer than one that gets only an average rating, even if the latter is heavier and larger. And with low fuel prices adding to an already swelling truck market, the safe-feeling high seating position of a crossover might not just be a placebo; if you’re at the same level as a lifted truck, you’re probably safer.
Ultimately, we could all probably stand to slow down a little bit, especially when coming up to an intersection, or when visibility is limited.
The difference between an impact at 100 km/h and at 130 km/h is significant, not to mention that you have a better chance of avoiding a crash in the first place if you slow down. The summation is a bit of a rockpaper-scissors affair; design trumps weight, but size still matters, as does speed. No matter what you drive, it’s a game you don’t want to lose.